1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. Further, the present invention relates to a process, a machine, manufacture, or a composition of matter. For example, in this specification, a semiconductor device, a method for driving the semiconductor device, and a method for manufacturing the semiconductor device are described. The present invention relates to a semiconductor device, for example, a circuit having a memory function of storing data, a processor including the circuit having the memory function, or an electronic device including the processor. Further, the present invention relates to a semiconductor device, for example, a display device or a light-emitting device.
Note that in this specification, a semiconductor device means a circuit including a semiconductor element (e.g., a transistor or a diode). The semiconductor device also means any device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip including an integrated circuit, a display device, a light-emitting device, and an electronic device are all semiconductor devices.
2. Description of the Related Art
A programmable logic device (PLD) is a kind of large integrated circuit (LSI), and is an integrated circuit whose internal circuit structure can be changed by a user with programming after shipment.
Fundamental components of the PLD are a plurality of logic elements performing logical operation and wirings connecting the logic elements to each other. The function of the PLD is changed by changing the function of each logic element and connection between the logic elements.
Data (configuration data) for setting the function of each logic element and the connection between the logic elements is stored in a memory device in the PLD. To write setting data to a memory device is referred to as configuration. A dynamic reconfiguration technology in which the circuit structure of a PLD is changed while a system including the PLD operates is known.
A multi-context method is known as a dynamic reconfiguration method. The multi-context method is a method for changing the circuit structure of a PLD by storing sets of configuration data corresponding to a plurality of circuit structures and switching the sets of configuration data to be used. A set of configuration data representing circuit structure data is referred to as a context.
With the downsizing of a PLD, an increase in power consumption due to an increase in leakage current becomes a problem. In order to solve the problem, for example, as disclosed in Patent Document 1, supply of power to unused or non-active circuit blocks is stopped by using a power gating switch. For example, as disclosed in Patent Document 2, supply of power to blocks that are independent of a circuit structure is stopped in accordance with the change in circuit structure by a programming cell including an oxide semiconductor.
Further, for example, as disclosed in Patent Document 3, the use of a memory including a transistor having an oxide semiconductor as a memory storing configuration data eliminates refresh operation.